New and improved processes have led to the more highly integrated and more reliable circuits which in turn have fueled the electronics industry. Process improvements allow for the fabrication of the circuits and chips into increasing densities and quantities with enhanced reliability characteristics. Structural improvements allow for greater circuit performance and control of power consumption with enhanced reliability as well. The advancement of chip density has led to the reduction of the size of the individual circuit components contained on the chip. These integrated-circuit chip densities have grown because of the ability to decrease the size of the individual devices (electronic components) contained on each chip. The benefits of the reduction in the size of the individual chip components have allowed for an increase in the circuit performance level because of the increased circuit speed. With the less distance the current must travel from component to component, the information contained therein can be processed within the chip in a shorter amount of time. More importantly, with density improvements the chip's circuits require less power to operate.
Although there are gains to be had from increasing component densities levels per chip, for the circuit designer these increased density levels have often led to increased frustrations concomitant with the design, development, and testing of the millions of circuit components contained on a single chip.
More particularly, in this art specific problems exist with establishing and maintaining proper bias conditions within the circuit which are independent of varying chip operating temperatures and differing supply voltage variations within the chip's many individual circuit components. In addition, additional problems are inherent in the manufacture of the chip wafer which may add process variations to the surface on which these many millions of components will be placed thereby changing resistances across the chip surfaces.
Because of the increasing complexity of the circuitry contained on a single integrated circuit (IC) chip, fluctuations in the current with temperature, supply voltage, and process variations can also often result in problems which may impact the design objectives of the particular circuit and its function. In other words, it is desirable in this art to be able to tighten circuit parameters given a wide variety of operating conditions and process variations effecting the source current.